The present invention in one of its aspects relates to capacitance circuits and particularly to ferroelectric capacitors. Ferroelectric capacitors and uses thereof in memory circuitry are described in U.S. patent application Ser. No. 069,390, filed July 2, 1987, in the name of Klaus Dimmler and S. Sheffield Eaton, Jr. (one of the inventors hereof), entitled "Ferroelectric Shadow RAM," filed simultaneously herewith now U.S. Pat. No. 4,809,225 issued Feb. 28, 1989 to Ramtron Corporation of Colorado Springs, Colorado the entire disclosure of which is hereby incorporated by reference, and in several issued U.S. patents such as Rohrer U.S. Pat. No. 3,728,694 for "Thin Film Ferroelectric Device" ad Rohrer U.S. Pat. No. 3,939,292 for "Process For Stable Phase III Potassium Nitrate And Articles Prepared Therefrom."
A certain combination of two ferroelectric capacitors having a common node has been referred to as a "transcharger" or a transpolarizer" in Polar Dielectrics by Burfoot and Taylor, pp. 291-93 (1979). This text indicates such transchargers as having a "blocked" state and an "unblocked" state. No specific mention is made in this reference of using such a configuration as a capacitance divider or of combining it with other circuit elements to form a memory cell, although it is reported that transchargers had been used to form "an associative memory."
An object of this invention is to employ an arrangement of ferroelectric capacitors as a capacitance divider useful in memory applications and elsewhere.
Another object of the present invention is to devise ferroelectric memory cells wherein decay of the ferroelectric properties is self-compensated.
A further object is to provide an improved "shadow" RAM over the circuit described in the abovereferenced Ferroelectric Shadow RAM patent application.
A specific object of this invention is also to provide a shadow dynamic RAM cell.
Still another object of this invention is to provide an improved dynamic RAM cell capable of use in both volatile and non-volatile modes.